Kinematic coupling

ABSTRACT

A kinematic coupling includes a male connector ( 94 ) and first and second opposed jaws ( 122, 124 .) Each of the jaws is pivotable from a retracted position in which the male connector can be inserted between the jaws and an engaging position in which the jaws prevent withdrawal of the male connector from between the jaws. The male connector is movable between an extended and a retracted position, and is biased towards the retracted position. This provides a positive clamping force when the kinematic coupling is engaged.

This invention was supported in part by grants from the Defense AdvancedResearch Projects Agency. The U.S. Government may have rights in thisinvention.

INTRODUCTION TECHNICAL FIELD

This invention particularly relates to a cartridge for use in theburn-in and/or test of circuitry formed on semiconductor wafers, beforethe wafer is diced. The invention may however also be applicable to theburn-in or test of other electrical devices. This invention furtherrelates to methods of loading and aligning a probe card in the cartridgewith a semiconductor wafer located in the cartridge. The invention alsorelates to a connecting device for use in the cartridge. This inventionis related to the inventions in commonly owned U.S. Pat. No. 5,429,510,issued to Barraclough et al. on Jul. 5, 1995, entitled “High-DensityInterconnect Technique,” and commonly owned U.S. Pat. No. 5,682,472,issued to Brehm et al. on Oct. 28, 1997 and entitled “Method and Systemfor Testing Memory Programming Devices,” the disclosures of which arehereby incorporated by reference herein. This invention is flirtherrelated to the invention in a concurrently filed, copending, commonlyowned application entitled “Wafer Level Burn-In and Electrical TestSystem and Method” (Attorney Docket No. AEHR-007/00US,) the disclosureof which is also incorporated by reference herein.

BACKGROUND OF THE INVENTION

It is well known that integrated circuits (IC's), if they are going tofail, tend to fail early in their projected lives. To identify andeliminate such fragile IC's, IC manufacturers typically expose theirintegrated circuits to conditions that tend to induce such prematurefailure. This is known as burn-in, and the typical conditions to whichthe integrated circuits are exposed during burn-in are elevatedtemperatures together with the simultaneous application of electricalsignals to the integrated circuits. The elevated temperature and theapplied signals may exceed normal operating parameters. Once anintegrated circuit has passed a test during or after burn-in, thechances of it functioning throughout its intended service life aregreatly increased.

Burn-in may be done at various times. In many cases, burn-in is donewhen the IC is in its final packaged form. In such a case, the IC isplugged into a circuit board that allows the required electrical signalsto be applied to the IC. Burn-in of packaged IC's has the advantage thatthe packaged IC is much less sensitive to physical damage orcontamination, and can easily be plugged into the burn-in circuit boardto make the required connections. Disadvantages of burning-in packagedIC's are that the added expense of packaging the IC is lost if the ICfails during burn-in, that there are many more individual components tohandle, and that the same die type may end up in a number of differentpackage types requiring different fixtures for burn-in.

Another burn-in option is to put individual dies into reusable packages,and then burn-in the die in the reusable package in a similar manner tothe burn-in of packaged IC's. This method has the advantage that lesshas been invested in the IC at this time, but has the disadvantage thatthe individual dies are difficult to handle conveniently, and aresusceptible to damage or contamination.

The cartridge of the invention is used for wafer-level burn-in. That is,the integrated circuit wafer undergoes burn-in before separation intoindividual dies and traditional packaging. Wafer-level burn-in has theadvantages that failure-prone IC's are identified early, that forcertain chip types (e.g., DRAM) there is the possibility oflaser-repairing burn-in defects, and that wafer maps of burn-in failuresare easily generated. Wafer maps assist in identifying and rectifyingwafer processing flaws. Wafer-level burn-in has the disadvantages thatcareful handling of the wafer is required, and that making electricalcontact with the wafer is more difficult. An example of a fixture usedfor wafer-level burn-in is shown in US Pat. No. 5,859,539 to Wood et al.

IC's also typically undergo functional tests at some point. These testsverify that the IC has the required functionality at the desired speedand accuracy. The functional tests can be used to reject IC's entirely,or may be used to classify IC's into different grades.

The cartridge of the invention may be used for wafer-level burn-inand/or testing.

SUMMARY OF THE INVENTION

According to the invention there is provided a method of burning-in ortesting a wafer, comprising the steps of placing the wafer on a chuckplate; aligning a probe plate with the wafer; and locking the chuckplate and the probe plate together. Preferably the step of placing thewafer on the chuck plate comprises the step of aligning the wafer withthe chuck plate to within a first tolerance and the step of aligning theprobe plate with the wafer is done to within a second tolerance, thefirst tolerance being greater than the second tolerance.

Also according to the invention there is provided a cartridge forwafer-level burn-in or test, comprising a chuck plate to receive awafer, a probe plate to establish electrical contact with the wafer, anda mechanical connecting device to lock the chuck plate and the probeplate fixed relative to one another. Preferably, the probe plateincludes a probe card movably coupled to the probe plate. Morepreferably, the probe card is mounted to the probe plate by at least twoleaf springs and there is a piston slidably located in a recess formedin the probe plate behind the probe card.

Yet further according to the invention there is provided a kinematiccoupling comprising a male connector including an undercut surface; andfirst and second opposed jaws. Each of the jaws is movable from aretracted position in which the male connector can be inserted betweenthe jaws and an engaging position in which the jaws prevent withdrawalof the male connector from between the jaws by engaging the undercutsurface of the male connector. Preferably the first and second jaws arebiased towards their respective engaging positions, and the first andsecond jaws each include an inclined surface that can be acted upon by akey to move the first and second jaws into their respective retractedpositions. More preferably, the male connector is movably coupled to asubstrate such that, when the male connector is inserted between thefirst and second jaws and the first and second jaws are both in theirengaging positions, the male connector is movable relative to thesubstrate between an extended position in which the engaging surface ofthe male connector is not in contact with the first and second jaws anda retracted position in which the engaging surface of the male connectoris in contact with the first and second jaws. Even more preferably, themale connector is biased towards its retracted position, thereby toprovide a positive clamping force.

Still further according to the invention there is provided a wafer levelburn-in or test cartridge, comprising:

a first plate;

a second plate;

a male connector that is mounted to the first plate, the male connectorincluding an undercut surface; and

at least one jaw that is movably coupled to the second plate, the jawbeing movable from a retracted position in which the male connector canbe received by the jaw and an engaging position in which the jawsprevent withdrawal of the male connector from the jaw by engaging theundercut surface of the male connector.

Further details of the invention are set forth in the section entitled:“Description of Specific Embodiments.”

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a wafer-level burn-in and test cartridgeaccording to the invention;

FIG. 2 is a partially cut away and exploded perspective view of theprobe plate of the cartridge shown in FIG. 1;

FIGS. 3 and 4 are two views of a leaf spring for use in the cartridge ofFIG. 1;

FIG. 5 is a partial cross sectional view through the cartridge of FIG.1;

FIG. 6 is a cross sectional view of the mechanical connecting device ofthe cartridge of FIG. 1;

FIG. 7 is a top view of the lower portion of the connecting device ofFIG. 6;

FIGS. 8A to 8D illustrate the actuation of the mechanical connectingdevice of FIGS. 6 and 7;

FIG. 9 is a schematic view of the relationship between the maleconnector and the jaws of the mechanical connecting device of FIG. 6.

FIGS. 10 to 12 are plan views of alternative configurations of the jawsof the mechanical connecting device of FIG. 6;

FIG. 13 is a cross-sectional view of the connector end of the probeplate of the cartridge of FIG. 1;

FIG. 14 is a schematic view of the underside of the probe plate of thecartridge of FIG. 1;

FIGS. 15 to 17 are plan views of isotherms on the upper surface of thechuck plate pedestal of cartridge of FIGS. 1-3;

FIG. 18 is an enlarged cross-sectional partial view of the chuck plate,piston, probe card and related components of the cartridge of FIG. 1;

FIG. 19 is a plan view of the lower surface of the alignment plug ofFIG. 18 to illustrate the shape and size of the epoxy bond between theprobe card and the alignment plug;

FIG. 20 is a perspective view of one corner of the cartridge of FIG. 1;

FIGS. 21 and 22 are perspective views of a cam plate for use with thecartridge of FIGS. 1 and 20;

FIG. 23 is a cross-sectional view illustrating the coupling between thecam plate of FIGS. 21 and 22 and a pneumatic cylinder; and

FIG. 24 is a perspective view of a mechanism for engaging anddisengaging the electrical connectors of the cartridge of FIG. 1 withcorresponding electrical connectors in a burn-in chamber.

DESCRIPTION OF SPECIFIC EMBODIMENTS

A wafer-level burn-in and test cartridge according to the invention isillustrated in FIG. 1. The cartridge, generally indicated by thereference numeral 10, comprises a chuck plate 12 and a probe plate 14.The chuck plate 12 and the probe plate 14 may be made of any suitablematerial. In the illustrated embodiment, the chuck plate 12 and theprobe plate 14 are made of 6061 aluminum.

The chuck plate 12 is generally rectangular in shape, and includes acentrally-located raised pedestal In use, a semiconductor wafer isplaced on the upper surface 18 of the pedestal 16. Mounted to the uppersurface of the chuck plate 12 are the lower halves 20 of threemechanical connecting devices that are used to lock the chuck plate 12and the probe plate 14 together in use. In the illustrated embodiment,the mechanical connecting devices are kinematic couplings, which arediscussed below in more detail with reference to FIGS. 6 to 12. Formedtransversely through the chuck plate 12 are a number of channels 22 thathave air or another fluid circulated through them in use to cool or heatthe chuck plate 12. Formed around the edges of the chuck plate 12 are anumber of handhold recesses 24 that encourage an operator to pick thechuck plate up away from the pedestal 16 or the lower halves 20 of themechanical connecting devices. The chuck plate 12 may also be providedwith vertical holes (usually three) extending between the upper surfaceof the pedestal and the bottom surface of the chuck plate 12. Such holesmay be used for the insertion of wafer-lift pins that are used in somewafer alignment systems.

The probe plate 14 is also generally rectangular in shape, and also hasa number of handhold recesses 26 formed in its upper surface 28 toencourage an operator to pick the probe plate 14 up away from thesensitive areas of the probe plate. Also shown on the upper surface ofthe probe plate are access covers 30 by means of which access can begained to the upper halves (not shown) of the mechanical connectingdevices.

Also shown on the probe plate 14 are a number of nipples 31, 33 wherebypneumatic connections can be made to the cartridge 10. Pneumatic and/orvacuum actuation is used in the operation of various parts of thecartridge as will be described in more detail below. While the actuationdescribed below is effected by varying the pressure of air, it will beappreciated that other fluids could also be used in the invention.

Located on each side of the probe plate 14 is a rail 32 (one sideshown.). Mounted in each rail are a number of vertically-oriented wheels34 and a number of horizontally-oriented wheels 36. The wheels 34, 36are mounted on shafts 38, and in the preferred embodiment the wheels aresmall ball bearings. In use, the rails 32 slide into correspondinglyshaped channels in a burn-in chamber, with the vertically-orientedwheels 34 supporting the cartridge 10 on the lower surface of thechannels and with the horizontally-oriented wheels preventing the rails32 from sliding against the sidewalls of the channels. The channels inthe burn-in chamber may extend beyond the ends of adjacent insertedcartridges, to further facilitate insertion of the cartridge in theburn-in chamber.

Located at one end of the probe plate 14 is a vertical flange 40.Attached to the flange 40 is a connector block 44 that has a number ofelectrical connectors 46 mounted thereto. In use, the electricalconnectors 46 are used to establish electrical connection with thewafer. Mounted to the flange 40 around the connector block 44 is a seal42. In use, the cartridge 10 is slid connector-side first into a hightemperature section of the burn-in chamber, until the connector block 44protrudes out of the high-temperature section into a lower temperaturesection through an aperture in a rear wall of the burn-in chamber. Theseal 42 then serves to seal against the wall around the aperture,thereby isolating the connector block from the conditions in thehigh-temperature section of the burn-in chamber. The connector block 44is made of a high temperature polymer such as Ultem, which is a thermalinsulating material that serves to insulate the electrical connectors 46from the high temperatures to which the flange 40 is exposed in use.Finally, mounted to the connecting block 44 are two alignment pins 48that serve to align the connectors 46 with corresponding electricalconnectors when the cartridge 10 is slid into the burn-in chamber.

FIG. 2 shows the underside of the probe plate 14, as well as a furthercomponent of the cartridge, the probe card 50. The probe card 50 is thepart of the cartridge that actually makes direct electrical contact withthe wafer during wafer-level burn in and/or test, and the probe card 50is thus different for each different type of wafer undergoing burn-inand/or test. The probe card 50 is electrically connected to theelectrical connectors 46 by means of printed circuit boards as isdescribed in more detail in the concurrently filed, copending, commonlyowned patent application entitled: “Wafer Level Burn-in and ElectricalTest System and Method” (Attorney Docket Number AEHR-007/00US,) thedisclosure of which is incorporated herein by reference.

The probe card 50 is preferably made of a material that is thermallymatched with the semiconductor material from which the wafer is made.That is, when heated, the probe card 50 and a wafer under test willexpand by similar amounts. This ensures that the electrical contactbetween the probe card 50 and a wafer under test is not disturbed as thecartridge is heated in a burn-in chamber. This permits the probe card 50to be aligned with the wafer when the wafer is at room temperature,before exposure to the elevated temperatures of burn-in. For example,the probe card 50 may be made of silicon-carbide, which provides a goodthermal match with a silicon wafer. However, it should be noted that theparticular details of the probe card 50 do not form part of theinvention, and currently available and future-developed probe cards 50can advantageously be used in the cartridge and methods of theinvention. For example, a probe card that is suitable for use in thecartridge and methods of the invention can be purchased from theElectronics Division of W. L. Gore & Associates, Inc. of Delaware.

The probe card 50 is mounted to the probe plate 14 by means of four leafsprings 52 that are spaced around the perimeter of the probe card 50.The leaf springs 52 permit relative motion between the probe plate 14and the mounted probe card 50 along the z-axis (that is, perpendicularto the surface of a wafer located on the pedestal 16). The leaf springs50 also permit the probe card to rotate to some degree relative to theprobe plate 14 around the x or y-axes (i.e., rotation aboutperpendicular axes both being parallel to the surface of the wafer). Theleaf springs 52 however prevent substantial movement of the probe card50 relative to the probe plate 14 along the x or y-axes, and alsoprevent substantial rotation of the probe card 50 relative to the probeplate 14 about the z-axis. Preferably, the leaf springs 52 are spacedabout the circumference of the probe card 50 to provide a substantiallymaximum resistance to rotation of the probe card relative to the probeplate about the z-axis. When the probe card is rectangular as shown,this is accomplished by locating a leaf spring 52 at or near each of thefour corners of the probe card 50.

This leaf spring mounting arrangement permits the probe card 50 to bemoved into and out of contact with a wafer located on the pedestal 16,and permits the probe card to “settle” evenly onto a wafer if one edgeor area of the probe card 50 contacts the wafer first. However,misalignment of the probe card 50 and the wafer is minimized duringapplication of the probe card to the wafer, since the leaf springs 52resist translation of the probe card 50 across the surface of the waferand also resist rotation of the probe card 50 around an axisperpendicular to the surface of the wafer.

One of the leaf springs 52 is shown in more detail in FIGS. 3 and 4. Ascan be seen from FIG. 4, the leaf spring 52 has a non-linear profile.More particularly the leaf spring 52 includes a curved central portion54 in the shape of a channel that extends across the width of the leafspring 52. The central portion 54 permits the leaf spring to deformpredictably under compression forces F that might otherwise cause theleaf spring 52 to buckle unpredictably. The central portion 54 alsoensures that the different leaf springs 52 behave in a substantiallyuniform manner under tension or compression, providing uniformcompliance around the probe card 50. The predictable compliance of theleaf spring under compression or tension also permits the mountingarrangement to compensate predictably for any changes in dimensionresulting from any mismatch of the thermal coefficients of expansion ofthe probe card and probe plate materials. The leaf spring 52 includesfour holes 56 defined therein whereby the leaf spring can be screwed tothe probe card and to the probe plate.

By way of example only, a leaf spring for use in the cartridge of theinvention has a width of 0.8″ (20.3 mm,) a length of 1.23″ (31.2 mm,) athickness of 0.010″ (0.254 mm) and the central portion 54 has anapproximate radius of 0.31″ (7.87 mm.). The leaf spring 52 is made ofberyllium copper, but may be made of any suitable spring material.

Returning now to FIG. 2, it can be seen that the probe plate 14 definesa recess 58 for receiving the probe card 50- The recess 58 includes fournotches for receiving the leaf springs 52.

Defined in the center of the recess 58 is a cylindrical recess 62 thatreceives a thin cylindrical piston 64. Defined in the center of therecess 58 is a further cylindrical recess 65 that has a sleeve 66mounted therein. When the probe card is mounted to the probe plate 14with the piston 64 received in the recess 62, a guide plug 68 mounted onthe back of the probe plate 50 is located in the sleeve 66. The guideplug 68 serves to provide additional alignment and guidance of the probecard 50 as it moves towards and away from the wafer.

The relationship between the probe card 50, the piston 64 and the probeplate 14 is shown in more detail in FIGS. 5 and 18. FIG. 5 also showsthe relationship in use between these components and the chuck plate 12,having a wafer 74 positioned thereon, and FIGS. 18 and 19 show how theprobe card 50 is mounted to the guide plug 68.

The probe card 50 is mounted to the guide plug 68 by means of an epoxybond 83. The epoxy used is typically a Loctite™ aerobic adhesive. Bymounting the probe card 50 at its center using a small area of epoxy 83,thermal mismatch between the probe card 50 and the rest of the cartridgeis minimized, since the probe card 50 is free to expand or contractrelative to the rest of the cartridge. To center the probe card 50relative to the alignment plug 68 during bonding, and to provide adegree of compliance between the alignment plug 68 and the probe card50, a strip of Teflon™ tape 81 is provided around the lowercircumference of the alignment plug 68.

As can be seen from the figures, the sleeve 66 has a cylindrical innerbore that receives the guide plug 68. Formed in the sleeve 66 are threegrooves—a groove 78 in the bore 70, a groove 80 in the upper surface ofthe sleeve 66 and a groove 82 in the stepped outer surface of the sleeve66. These three grooves have O-rings received therein as shown.Similarly, the piston 64 has one groove 84 formed in its edge(circumference) and one groove 85 formed in its lower surface. Thesegrooves in the piston also have O-rings received therein. These fiveO-rings serve to provide an airtight seal between the 30 space 72 behindthe piston and the general vicinity of the wafer. Accordingly, byincreasing the air pressure in space 72 behind the piston 64, the piston(and hence the probe card 50) can be advanced towards the wafer 74.Similarly, by reducing the pressure in space 72, the piston 64 (andhence the probe card 50) can be retracted from the wafer 74. This isdone via a conduit formed in the probe plate between the space 72 andone of the nipples 31 located on the exterior of the probe plate 14.

Alternatively, if the pressure in the space 72 is left unchanged, thepiston can be moved by varying the pressure in the general vicinity ofthe wafer 74, thereby creating a pressure differential between differentsides of the piston 64 as before, except reversed in action. That is, bydecreasing the air pressure in the general vicinity of the wafer 74, thepiston (and hence the probe card 50) can be advanced towards the wafer74. Similarly, by increasing the pressure in the general vicinity of thewafer 74, the piston 64 (and hence the probe card 50) can be partiallyretracted from the wafer 74. Manipulation of the air pressure in thevicinity of the wafer 74 is done via a conduit formed in the probe plate14 that provides fluid communication between one of the nipples 31 and aregion 79 behind the guide plug 68 (see FIG. 18). The region 79 is inturn in fluid communication with a region between the piston 64 and theprobe card 50 via an axial bore 87 and one or more transverse bores 88formed in the guide plug 68. The area between the probe card 50 and thepiston 64 is in turn in fluid communication with the immediate vicinityof the wafer 74 via a hole 89 formed in the probe card 50. Thus, whenthe pressure in the region 79 is reduced, there is a correspondingreduction in the pressure in the vicinity of the wafer 74. If the piston64 is to be moved by a reduction of the air pressure in the vicinity ofthe wafer 74, an O-ring 75 is provided in an annular groove 76 definedin the upper surface 18 of the pedestal 16. The probe card 50 abuts theO-ring 75 in the groove 76 to seal the area in the vicinity of the wafer74. The use of an O-ring 75 in the groove 76 also assists in maintainingcleanliness of the wafer 74.

As an alternative to the routing described in the previous paragraph forreducing the pressure in the vicinity of the wafer 74, the vacuum pathmay travel for a short distance in the probe plate 14 from the nipple 31before being transferred to the chuck plate 12 by means of a pneumaticseal. The vacuum would then be conveyed through the chuck plate 12 tothe vicinity of the wafer 74 via a passage formed in the chuck plate 12.

The nipples 31 that are used in the control of the movement of thepiston 64 are of the type that close when the pneumatic lines coupled tothe nipples 31 are removed. This means that after the probe card 50 isadvanced against the wafer 74 with the required probe actuation force,the cartridge can be disconnected from the pneumatic lines, and therequired probe actuation force is then maintained independently by thecartridge 10. This has the advantage that the burn-in of the wafer canbe done separately from the expensive equipment required to align thewafer and probe card, and a separate mechanism to provide the probeactuation force is not required. It should be noted however thatpneumatic connection with the cartridge 10 is typically reestablished inthe burn-in chamber. This permits the various pressure differentials tobe maintained (in case of leaks,) and also permits the pressuredifferentials to be maintained constant as the cartridge is heated orcooled.

The cartridge also includes three mechanical connecting devices 90 asshown in more detail in FIG. 6. The connecting devices 90 are used toclamp the chuck plate 12 and the probe plate 14 together. The connectingdevice 90 comprises a lower portion 20 and an upper portion 92 that arelocated as shown in FIGS. 1, 2 and 14. While the terms “upper” and“lower” are used here for convenience, it will be appreciated that thesetwo portions of the connecting device may be used in any functionalorientation.

The upper portion 92 of the connecting device includes a male connector94. The male connector 94 includes a head 96 and a neck 98. At the baseof the neck 98, the male connector defines a cylindrical piston 100whereby the male connecting device is movably mounted to the substrate102. In the illustrated embodiment, the substrate 102 is the probe plate14. Located in a groove 104 defined in the edge of the piston 100 is aseal 106 that serves to seal the interface between the piston 100 andthe substrate 102. Located in an annular groove 108 around the neck 98of the male connector are several Belleville springs 110. The head 96defines an undercut surface 114, and is mounted to the neck 98 by meansof a bolt 112. On either side of the piston 100 are cover plates 116 and118 that are mounted to the substrate 102. The springs 110 bearrespectively against the bottom surface of the groove 108 and the coverplate 116, thereby to bias the male connector 94 into a retractedposition. Defined between the piston 100, the cover plate 118, and thesubstrate 102 is a space 118. The space 118 is connected to the nipples33 shown in FIG. 1 via a conduit 120. By introducing high-pressure airinto the space 118 via the conduit 120, the male connector 94 can beadvanced against the bias of the springs 110 into an extended position.

Referring now to FIGS. 6 and 7, the lower portion 20 of the mechanicalconnecting device 90 is seen to include first and second opposed jaws122, 124. The jaws 122, 124 are pivotally mounted to the chuck plate bymeans of pivot pins 126. This mounting arrangement permits the jaws122,124 to pivot from a retracted position (shown in FIG. 6) in whichthe male connector 94 can be inserted between the jaws 122, 124, and anengaging position (shown in FIG. 8C) in which the jaws 122, 124 preventwithdrawal of the male connector 94 therefrom by engaging the undercutsurface 114 of the male connector 94. The jaws are biased towards theirengaging position by means of two spring plungers 125 that are locatedin threaded bores 127 formed in an inclined wedge 142. The springplungers each have a threaded outer surface that permits them to beselectively positioned in the bores 127.

The first and second jaws 122, 124 each include an inclined surface 128that can be acted upon by a key or probe 130 to move the jaws 122, 124from their engaging positions into their retracted positions. The probeor key 130 includes a spherical head 132, and is inserted through a holedefined in the chuck plate 12. The jaws 122, 124 each include aprotruding lip 136 that has an undercut surface 138 that engages theundercut surface 114 of the male connector 94 in use. As can be seen inFIG. 7, the front surface of the lip has circular notch formed thereinso that the head 96 can be received without undue retraction of the jaws122, 124.

Surrounding the jaws 122, 124 is an adjustable stop 140. The adjustablestop 140 is mounted on top of the inclined wedge 142 by means of fourscrews 144. The screws 144 pass through slots 146 defined in two flanges148 that extend from the lower edges of the stop 140. The wedge 142 ismounted to the chuck plate 12 by means of four bolts 152. The upperedges of the stop include central raised portions 154 against which acorresponding raised portion 156 of the cover plate 116 abuts when theconnecting device 90 is engaged as will be described in more detailbelow.

An adjusting mechanism 158 is mounted at one end of the wedge 154. Theadjusting mechanism 158 includes an internally threaded barrel 160 andan externally threaded rod 162. The rod 162 has a hexagonal recessdefined therein by means of which an allen wrench can be used to rotatethe rod, thereby to advance or retract it. The rod 162 has a groove 164defined therein that permits one end of the rod to be received by avertical, T-shaped groove 166 in the stop 140. To adjust the height ofthe raised portion 156 above the chuck plate 12, the screws 144 areloosened and the rod 160 is rotated to advance or retract the stop 140along the inclined wedge 142. When the desired adjustment has been made,the screws 144 are retightened. By adjusting the stops 140 of all threelower portions 20 of the mechanical connecting devices 90, the distancebetween the chuck plate 12 and probe plate 14 (when they are clampedtogether) can be varied. Referring to FIG. 5, it will be appreciatedthat this adjustment permits the cartridge to be adapted to probe cardsand wafers of different sizes, and also to make fine adjustments to therelationship between the wafer 74 and the probe card 50.

While the mechanical connecting device 90 has been described as having aconfiguration that has the male connector 94 normally retracted, and thejaws 122, 124 normally closed, it will be appreciated that thisarrangement may be varied to provide a male connector that is normallyextended and jaws 122, 124 that are normally open.

The sequence of operation of the mechanical connecting device 90 isshown in FIGS. 8A to 8D. As shown in FIG. 8A, the key or probe 130 isadvanced between the first and second jaws 122, 124 against the inclinedsurfaces 128, thereby to move the jaws 122, 124 from their engagingpositions into their retracted positions. The space 118 is pressurizedto advance the piston 100 (and hence the male connector 94) in thedirection of the chuck plate 12. The chuck plate 12 and the probe plate14 are then moved together to position the head 96 of the male connectorbetween the jaws 122, 124 as shown in FIG. 8B. The clearances betweenthe head 96 and the retracted jaws 122, 124 is sufficient to allowlateral misalignment (i.e., in a direction parallel to the surface ofthe wafer 74) of the chuck plate 12 and the probe plate 14 in an amountthat is greater than the expected variation in the positioning accuracyof the wafer on the chuck plate 12. In the illustrated embodiment, theconnecting mechanisms 90 can be engaged over a range of relative lateralmovement of the chuck plate 12 and the probe plate 14 of +/−0.05″(+/−1.27 mm). As will be discussed in more detail below, this permitsthe wafer 74 to be positioned relatively crudely on the pedestal 16.Accurate alignment of the probe card 50 with the wafer is then donedirectly—by aligning the probe plate 14 with the wafer 74—without havingto be concerned about bow the probe plate 14 and chuck plate are goingto mate. The probe plate 14 and the chuck plate 12 can then be lockedtogether to maintain the alignment between the probe plate 14 and thewafer 74. Aligning the probe plate 14 directly with the wafer 74 in thismanner avoids the buildup of tolerances that would occur if the waferwas aligned indirectly with the probe plate 14 by first aligning it withthe chuck plate 12 and then aligning the probe plate 14 with the chuckplate 12.

Exemplary figures for the tolerance required of the alignment betweenthe wafer 74 and the probe card 50 are the same as those for alternativewafer-level burn-in and test solutions, e.g., +/−0.001″ (+/−12.5 micron)(based on the Gore probe card alignment pad 30 geometry,) +/−0.0005″(+1.25 micron) (for NHK pogo pin adapter plate pin placement.). It willhowever be appreciated that the tolerance required of the alignmentbetween the probe card 50 and the wafer 74 is dependant on theparticular type of integrated circuit formed on the wafer, the size andpitch of the contact pads on the wafer, and the particular probe cardbeing used. As feature sizes decrease in semiconductor devicefabrication, the required alignment tolerances will decrease in acorresponding manner. Accordingly, it should be noted that the figuresquoted above are only examples used to illustrate the generalrelationship between the coarse alignment of the wafer on the chuckplate 12 and the fine alignment between the probe card 50 and the wafer74.

As can be seen from FIG. 8C, the probe or key 130 is then withdrawn frombetween the jaws 122, 124, thereby to permit the jaws 122, 124 to returnto their engaging positions. The space 118 behind the piston 100 is thendepressurized and the male connector 94 is retracted under the biasingeffect of the springs 110, as shown in FIG. 8D. As the male connector 94retracts, the undercut surface 114 of the male connector 94 engages theundercut surfaces 138 of the jaws 122, 124. This draws the chuck plate12 and the probe plate 14 together, until the central raised portion 154of the stop 140 abuts the raised portion 156 of the cover plate 116. Itshould be noted that in the engaged position of the mechanicalconnecting device 90 shown in FIG. 8D, the springs 110 are stillcompressed, which provides a positive clamping force between the chuckplate 12 and the probe plate 14. In the illustrated embodiment, theclamping force of each mechanical connecting device when fully engaged,as shown in FIG. 8D, is between 165 and 230 pounds (735 to 1020 N,) toprovide a total clamping force of 500 to 700 pounds (2.2 to 3.1 kN) forthe cartridge 10. When filly engaged, the probe plate 14 and the chuckplate 12 are prevented from separating by this clamping force, and areprevented from translating relative to one another by frictionalengagement of the surfaces 154 and 156. Frictional engagement betweenthe probe card 50 and the wafer 74 also assist in preventing the probeplate 14 and the chuck plate 12 from translating relative to oneanother.

It should also be noted that the springs 110 also assist in preventingthe buildup of undesirable thermal stresses in the clamped cartridge,since the springs 100 permit movement of the male connector 94 inresponse to any thermally-induced changes of dimension along thelongitudinal axis of the male connector 94.

To disengage the mechanical connecting device, the procedure describedabove with reference to FIGS. 8A to 8D is executed in reverse.

FIG. 9 is a schematic representation of the relationship between thejaws 122, 124 and the male connector 94 when they are engaged as shownin FIG. 8D. When engaged, it can be seen that there are clearances “a”and “b” between the neck 98 and the edges of the lips 136, andclearances “c” and “d” between the outermost edge of the head 96 and theinner surfaces of the jaws 122, 124. These clearances permit the jaws122, 124 to engage the head 96 undisturbed even when there is variationin the left-right (in FIG. 9) positioning of the male connector 94between the jaws 122, 124. Similarly, it will be appreciated that themale connector can be misaligned in a direction perpendicular to theplane of FIG. 9, within limits, without affecting the engagement of thejaws 122, 124 with the head 96. This permits the connecting mechanisms90 to be engaged over a range of relative lateral movement of the chuckplate 12 and the probe plate 14, as discussed above and below. In theillustrated embodiment, the total lateral misalignment of the chuckplate 12 and the probe plate 14 that can be tolerated by the connectingmechanisms 90 is +/−0.05″ (+/−1.27 mm).

The lip 136 of the jaws 122, 124 may have any one of a number ofdifferent profiles, examples of which are shown in FIGS. 10 to 12. Asshown in FIG. 12, the lip 136 may have a profile that defines arelatively sharp edge 170 for contacting the undercut surface 114 of themale connector 94 along a single line. Alternatively, the lip 136 mayhave a semi-cylindrical profile 172 as shown in FIG. 11 that will alsoprovide line contact between the lip 136 and the undercut surface 114 ofthe male connector 94. Yet further, the lip 136 may include a sphericalprotrusion 174 as shown in FIG. 12 that provides point contact with theundercut surface 114 of the male connector 94. While these features andshapes have been shown on the jaws 122, 124, it will be appreciated thatthese or similar features or profiles may be provided on the undercutsurface 113 of the male connector 94. Applicants believe that providingline or point contact between the jaws 122, 124 and the undercut surface114 of the male connector 94 helps prevent the creation of lateralforces during the engaging process described above with reference toFIGS. 8A to 8D. Lateral forces may cause lateral motion of the probeplate 14 and the chuck plate 12, potentially resulting in misalignmentof the probe plate 14 and the wafer 74, which is to be avoided.

It should be noted that while the jaws 122, 124 are pivotally mounted tothe chuck plate 12, there are alternatives to this arrangement. Forexample, the jaw(s) may comprise sliding members that are movablebetween two positions in which the male connector respectively can andcannot be retracted. Also, the jaw may take the form of a plate that hasa keyhole-shaped aperture therein, the male connector being insertablein the larger part of the aperture, and being prevented from beingwithdrawn when the plate is moved relative to the male connector 94 toposition the neck 98 of the male connector in the smaller part of theaperture. Accordingly, the term “jaw” can be applied to any arrangementthat selectively permits the reception and retention of the maleconnector.

It is also to be noted that the mechanical connecting device 90 is akinematic coupling. A kinematic coupling provides forces or movements incontrolled and predictable directions. The connecting device 90 isdesigned to provide motion and a clamping force only in the Z-direction(perpendicular to the wafer) during engagement. By providing forces andmovement only in the Z-direction, misalignment between the probe plate14 and the wafer 74 as a result of the actuation of the clamping deviceis reduced. Aspects of the mechanical connecting device 90 thatcontribute to its kinematic nature are the fact that the jaws 122, 124are pivotally mounted to the chuck plate 12, the fact that there is lineor point contact between the head 96 and the jaws 122, 124, the factthat the male connector 94 moves only in the Z-direction, and the factthat transverse motion between the probe plate 14 and the chuck plate 12is resisted by frictional engagement between two flat surfaces 154, 156that are perpendicular to the Z-direction.

As mentioned before with reference to FIGS. 1 and 2, the probe card 50is electrically connected to the electrical connectors 46 by means oftwo printed circuit boards. FIGS. 13 and 14 show the configuration ofthe printed circuit boards and how they are connected to the connectors46 and the probe card 50.

FIG. 13 is a partial longitudinal cross-sectional view through the probeplate 14, showing the connector block 44, the connectors 46, the flange40 and the seal 42. As can be seen from the FIG. 13, the connectors 46include upper connectors 180 and lower connectors 182. The connectors180, 182 are described in more detail in the concurrently filed,copending, commonly owned patent application entitled: “Wafer LevelBurn-in and Electrical Test System and Method” (Attorney Docket NumberAEHR-007/00US,) the disclosure of which is incorporated herein byreference.

The upper connectors 180 are mounted to the connector block 44 by meansof a spacer block 184 and an alignment pin 186. The alignment pin 186serves to align the upper connectors 180 with the lower connectors 182.The single alignment pin 186 is located centrally along the spacer block184 in a direction transverse to the plane of FIG. 13, to accommodatethermal mismatch between the connector block 44 and the spacer block184. Additional fasteners (not shown) are provided to hold the connectorblock 44 and the spacer block 184 together. These additional fastenersare spaced laterally apart from the alignment pin 186, and preferablyallow for some movement between the spacer block 184 and the connectorblock resulting from temperature fluctuations. An example of anadditional fastener that can be used is a small nut and bolt combinationthat has spring or wave washers at each end to engage the surfaces ofthe components to be fastened The spring or wave washers provide aclamping force while permitting some movement during relative motionresulting from thermal mismatches between the connector block 44 and thespacer block 184.

Each of the connectors 180 is mechanically and electrically connected toa rigid printed circuit board 188 that passes through a slot 190 formedin the flange 40 to the underside of the probe plate 14. Each of theconnectors 182 is mounted to the connector block 44, and is mechanicallyand electrically coupled to a bendable printed circuit board 192. Thebendable printed circuit board 192 passes through a slot (not shown)defined between the spacer block 186 and the connector block 44, andthen passes - together with the rigid printed circuit board 188 -through the slot 190 to the underside of the probe plate 14. The rigidprinted circuit board 188 is used to provide signals to and from thewafer under test, and the bendable printed circuit board is used toprovide power to the wafer under test.

FIG. 14 is a schematic view of the underside of the probe plate 14. Ascan be seen from the figure, the bendable printed circuit boards 192,after passing through the flange 40, extend on either side of the probecard 50 in a generally L-shaped configuration. Located beneath eachbendable printed circuit board 192 is the rigid printed circuit board188 that extends in a similar manner around the probe card 50. Theprinted circuit boards are held against the probe plate 14 by means of anumber of appropriately positioned screws. Electrical connection withthe probe card 50 is made by a number of flexible interconnections 196.The interconnections 196 are sufficiently flexible to accommodate themovement of the probe card 50 in use.

The manner in which electrical connections are made in and with thecartridge of the invention is described in more detail in theconcurrently filed, copending, commonly owned patent applicationentitled: “Wafer Level Burn-in and Electrical Test System and Method”(Attorney Docket Number AEHR-007/00US,) the disclosure of which isincorporated herein by reference.

Referring again to FIGS. 1 and 5, it can be seen that the chuck plate 12has features specific to its tasks of locating a wafer and provingthermal management of the wafer during burn-in or test. Formed in thechuck plate 12 are a number of channels 22. When the cartridge 10 islocated in use in a burn-in chamber, fluid is ducted through thesechannels 22 to remove heat dissipated by the wafer during burn-in. Thechannels 22 may be interrupted and staggered to further promote beattransfer, and may also be interrupted for access to various mechanicalfeatures necessary for the operation of the cartridge. As an alternativeto forming the channels 22 in the chuck plate 12, the chuck plate 12 maybe placed in contact with a separate plate in the burn-in chamber thathas fluid channels formed therein.

The overall size and shape of the chuck plate 12 are determined fromwafer size, as well as space considerations in the existing burn-inchamber configuration. In use, a wafer is placed on the upper surface 18of the pedestal 16. The upper surface 18 is polished and lapped to ahigh degree of smoothness and flatness. It also includes vacuum grooves19 for wafer restraint. This upper surface 18 receives plating orcoating appropriate to the type of wafer under test. Protruding into theside of the pedestal 16 (radially) are a number of bores that receivecartridge heaters 21. These supply heat for some modes of operation, inorder to achieve temperature control. A temperature sensor 23 isinstalled in the chuck near its top surface, to indirectly sense wafertemperature. In addition to these features, additional features specificto achieving temperature uniformity will be discussed below.

Temperature control of the wafer is accomplished as follows. The airfrom the burn-in chamber is ducted through the channels 22 of the chuckplate 12, while a powered wafer is pressed against the top surface bythe probe card 50. The chamber is set for a temperature calculated usingthe characteristics of the chuck plate system and the wafer powerdissipation. Fine control of temperature is from heat addition using theaforementioned cartridge heaters 21. A standard temperature controlleris used to supply power to these heaters and, by receiving input fromthe temperature sensor 23, the temperature controller provides active,closed loop feedback control of the temperature of the pedestal 16.

Power to the heaters 21 and the signal from the temperature sensor 23 isalso routed through the connectors 46. From the connectors 46,electrical connection is passed to contact pads on the chuck plate 12via pogo pins mounted on the probe plate 14. From the contact pads,electrical connection is made with the heaters 21 and the temperaturesensor via one or more flexible printed circuit boards that wrap aroundthe pedestal 16.

It will be appreciated that the flow of heat in use, and the resultingtemperature profiles in the chuck plate 12 may be less than ideal. Inparticular, it is desired to have a uniform and flat temperature profileacross the upper surface 18 of the pedestal 16 of the chuck plate 12.The chuck plate 12 is aluminum. Heat conducts through metallic objectsvery well, but an object designed with mechanical constraints will (inall likelihood) have an unsuitable temperature distribution on thespecified surface. Heat conducts (and convects) through air orders ofmagnitude more poorly than through metals. The embodiment of the chuckplate 12 described herein introduces precisely dimensioned regions ofmetal removal that change the effective conductivity of the metallicobject in certain regions and/or directions, thus allowing temperaturedistribution to be decoupled from the chuck plate's exterior physicaldimensions and thermal boundary conditions. The result is the ability totailor the temperature distribution on a given surface to a broad rangeof functions and/or values.

As mentioned before, the wafer 74 rests on the upper surface 18 of thepedestal 16, as shown in FIG. 5. This surface experiences a heat flux,due to power dissipated by the wafer 74 that rests upon it. Theconfiguration of the chuck plate 12 allows this surface to be morenearly isothermal, even though the outline dimensions thereof werechosen for mechanical reasons.

Thermal management of the chuck plate 12 is assisted by the use of oneor more precisely dimensioned grooves parallel to the upper surface 18,extending around the circumference of the pedestal 16. As shown in FIG.5, in the illustrated embodiment of the invention, one such groove isprovided—a lower groove 198. It should be noted that an upper groove 200is also formed in the chuck plate 12, but this groove is only used forthe routing of electrical wiring to and from the cartridge heaters andtemperature sensor, and does not contribute to the thermal management ofthe chuck plate. Heat flowing into the outer regions of the uppersurface 18 is forced to travel radially inward by the groove 198, thusraising the edge temperature (which would naturally be lower than thecenter). For a properly sized and shaped groove 198, it is possible toachieve a nearly constant-temperature top surface 18.

FIGS. 15-17, showing isothermal lines on the upper surface 18 of thepedestal 16, are useful for a more complete understanding of theoperation of the thermal management features of the cartridge of theinvention. FIG. 15 shows elliptical isothermal lines 238 formed in theupper surface 18 of the pedestal 16 in the absence of thermal managementfeatures. The temperature of each isothermal line 240 is shown in ° C.Elliptical isothermal lines typically occur as a result of an aspectratio effect of the length of the chuck plate 12 (along the channels 22)to the width of the chuck plate (across the channels 22.) To turn theelliptical isothermal lines into circular isothermal lines, the depth ofthe groove 198 may be varied as it passes around the pedestal. Dependingon the particular geometry of the chuck plate, the isothermal lines maynot be elliptical. FIG. 16 shows such a case, where the isothermal linesare generally circular. In such a case it is not necessary to vary thedepth of the groove 198. As shown in FIG. 17, when the appropriategroove 198 is provided, isothermal lines 242 have an essentiallycircular shape, and the upper surface becomes essentially isothermal, byraising the temperature adjacent to the outer edge of the pedestal 16.

In practice, burn-in of integrated circuits is usually carried out at125-150° C. In one typical cycle, the integrated circuits are heated to125-150° C. for 6 hours, followed by electrical test for one-half hourat 70° C. During burn-in of a typical dynamic random access memory(DRAM) integrated circuit wafer, electrical signals supplying about 500watts of power are supplied to the wafer. If the groove 198 is notprovided on the thermal chuck, there is approximately a 3 degreevariation in the temperature over the surface of the pedestal 16. Withthe appropriate groove 198 on the chuck plate 12, there is less than aone degree variation in the temperature over the surface of the pedestal16. At higher power levels, the temperature variation over the surfaceof the pedestal 16 is more significant. For example, some logic devicesrequire application of electrical signals producing a power input inexcess of 1 kilowatt to the wafer. Certain logic devices require powerinputs as high as 1.5 kilowatt. At 1.5 kilowatt of power to the wafer,if the groove 198 is not provided on the chuck plate 12, there isapproximately a 10° C. variation in the temperature over the surface ofthe pedestal 16 under these conditions. Such a temperature variation isa significant problem. With the groove 198 on the chuck plate 12, thereis only a two-degree variation in the temperature over the surface ofthe pedestal 16 under these conditions.

In a specific example, for use with an 8 inch (200 mm) semiconductorwafer and length (along the channels 22) and width (across the channels22) of the chuck plate of 18.72 inch (475 mm) and 16.5 inch (419 mm)respectively, with a pedestal height of 0.865 inch (22.0 mm,) the groove198 is 0.062 inch (1.57 mm) high and 1.043 inch (26.49 mm) deep. For theillustrated cartridge, Applicants found that the isothermal lines werein fact not elliptical, and it was thus not necessary to vary the depthof the groove 198 as it passes around the pedestal 16.

Variation of the characteristics of the groove can however be a usefultechnique for tailoring the shape of the isothermal lines to theparticular thermal characteristics of the cartridge system. For example,fluid in the channels 22 is going to rise in temperature as it flowsalong the channels 22, as a result of the heat that is being transferredto the fluid. As a result of this increase in temperature, the heattransfer to the fluid is going to be diminished along the length of thechannels 22. This may result in an undesirable temperature gradientforming on the pedestals along the length of the channels 22. This canbe compensated for by making the groove deeper at the entry side of thechannels, or by providing additional grooves, or by tailoring the groovein other ways.

The particular characteristics of the groove 198 will vary depending onthe particular characteristics and operation of the burn-in system. Todetermine the parameters of the groove for a particular burn-in systemoperated in a particular way, a computer-based heat transfer model ofthe chuck plate is generated, and the heat transfer characteristics ofthe chuck are modeled. Appropriate characteristics of the chuck plate inthe heat transfer model will then be adjusted (e.g., the depth andvariation in the depth of the groove) until the model demonstratesacceptable thermal characteristics. At that time, a prototype will bebuilt and tested in the lab to verify the computer-based model. If theprototype demonstrates acceptable thermal characteristics, the geometryof the prototype will be adopted. If not, further adjustments will bemade to the thermal model and the prototype, or just the prototype,until acceptable thermal characteristics are demonstrated by theprototype.

The chuck plate 12 is fabricated from a high thermal conductivitymaterial, such as aluminum or other suitable metal or other material. Itmay either be integrally formed by machining a single piece of thematerial or assembled by fastening separate pieces of the materialtogether to give the configuration shown. Preferably the chuck plate 12is formed integrally, since the absence of interfaces betweensub-components increases the efficiency of the heat transfer between theupper surface 18 of the chuck plate 12 and the fluid in the channels 22.In particular, this permits air to be used as a heat transfer fluid inthe channels 22 at a higher wafer power dissipation level than wouldotherwise be possible, before requiring the use of a liquid coolant. Theuse of a gas coolant is more convenient than the use of a liquidcoolant.

The loading of a wafer into the cartridge 10 will now be described.Firstly, the chuck plate 12 and the probe plate 14 are put into analignment system. The alignment system will include appropriatepneumatic or vacuum connections for supplying pressurized air or suctionto accomplish movement of the pistons 64 and 100, and to retain thewafer 74 on the pedestal 16.

Once the chuck plate 12 has been inserted in the alignment system, wafer74 is placed on the upper surface of the pedestal. The positioning ofthe wafer on the pedestal can be done relatively crudely (e.g. within atolerance of +/−0.005″ (+/−0.127 mm) since the ability of the mechanicalconnecting devices 90 to accommodate misalignment between the probeplate 14 and the chuck plate 12 permits the fine alignment of the probeplate 50 to be done with reference directly to the wafer, without havingto worry about precise alignment of the probe plate 14 with the chuckplate 12. The positioning of the wafer 74 on the pedestal 16 can be doneusing a known automatic wafer prealignment device that typicallyincludes robot arms and a center and notch or flat finder. Theprealignment device aligns the wafer 74 on the pedestal 16 in both x andy directions, and rotationally (theta) using a notch or flat in thewafer. Alternatively, alignment of the wafer on the chuck can beaccomplished using a known manual alignment fixture.

Once the wafer 74 has been placed on the upper surface 18 of thepedestal 16, a vacuum is supplied to the grooves 19 underneath the wafer74, thereby to retain the wafer securely on the pedestal 16. The airpressure in the space 72 behind the piston 64 is also reduced,retracting the piston 64 and the probe card 50 away from the wafer 74.

A vision capture system then captures images of the wafer and of theprobe card, and calculations are performed by the alignment system todetermine what movements are required to align the probe card 50 and thewafer 74. The precise alignment of the probe card 50 and the wafer 74 isthen done. This can either be done by movement of either the probe plate14 or the chuck plate 12, or by repositioning the wafer using wafer liftpins extending through holes formed in the chuck plate.

As an alternative, it is possible to capture an image of the wafer 74while it is being held by a wafer handling robot, and then to positionthe wafer 74 onto the pedestal 16 in the correct alignment with theprobe card 50. In such a case, the alignment and placing of the wafer 74take place in one step. However, in this case the precise alignment ofthe wafer is still being done with reference to the probe card 50/probeplate 14, and not with reference to the chuck plate 12.

After the probe card 50 (and hence the probe plate 50) has been alignedwith the wafer 74, the jaws 122, 124 of the mechanical connectingdevices 90 are moved into their retracted positions by advancing theprobe or key 130 between the jaws 122, 124 as described above withreference to FIG. 8. The space 118 is pressurized to advance the piston100 (and hence the male connector 94) in the direction of the chuckplate 12. The chuck plate 12 and the probe plate 14 are then movedtogether by the alignment device. This movement is done, as far as ispossible, in the Z-direction only, so that the alignment of the probecard 50 and the wafer is not disturbed. The probe plate 14 and the chuckplate 12 are moved together until the heads 96 of the male connectors 94of the three mechanical connecting devices 90 are positioned between thejaws 122, 124 as shown in FIG. 8B.

The probe or key 130 is then withdrawn from between the jaws 122, 124,thereby to permit the jaws 122, 124 to return to their engagingpositions. The space 118 behind the piston 100 is then depressurized andthe male connector 94 is retracted under the biasing effect of thesprings 110. As the male connector 94 retracts, it engages the jaws 122,124, thereby to draw and lock the chuck plate 12 and the probe plate 14firmly together, with the central raised portion 154 of the stop 140abutting the raised portion 156 of the cover plate 116.

After actuation of the mechanical connecting devices 90, the piston 64may be advanced to press the probe card 50 against the wafer 74.Alternatively, the piston 64 may be advanced or retracted (or, morecorrectly, the pressure differential across the piston 64 is varied) toadjust the initial probe actuation force. Actuation of the piston 64 isdone by creating a pressure differential in the cartridge 10, which canbe done in one of two ways.

Firstly, the pressure in the space 72 can be steadily increased, therebyto advance the probe card 50 against the wafer 74. The maximum pressurein the space 74 is selected to provide the desired probe actuationforce. The desired probe actuation force is wafer and probe cardspecific, but is typically approximately 500 pounds (2.2 kS) for an 8inch (200 mm) wafer.

Secondly, the air pressure in the space 74 can be normalized to ambientpressure before or at the same time as the air pressure in the vicinityof the wafer is reduced. In such a case, a seal is provided in thegroove 76 as described above. By reducing the pressure in the vicinityof the wafer 74, the piston 64 and probe card 50 are sucked down ontothe wafer. Again, the amount of pressure reduction in the vicinity ofthe wafer (or more correctly, the pressure differential across thepiston 64) is selected to provide the desired probe actuation forces.

While reducing pressure in the vicinity of the wafer 74 and increasingthe pressure in the space 72 are acceptable alternatives for actuatingthe piston 64, Applicants believe that reducing the pressure in thevicinity of the wafer is the best mode of providing the probe actuationforce, since the reaction forces generated thereby are self-contained atthe wafer, probe card 50 and pedestal 16. This is in contrast to raisingthe pressure in space 72, which tends to push the probe plate 14 andchuck plate 12 apart when the probe card 50 bears against the wafer 74.This would cause some deflection of the probe and chuck plates.

There are a number of more specific methods of locking the chuck plate12 and the probe plate 14 together and providing a probe actuationforce, as will be discussed below. For purposes of conciseness, the stop140 (with its central raised portion 154) and the raised portion 156 ofthe cover plate 116 will now be referred to collectively as “the stops,”having a combined “stop height.”

Method 1

The alignment device moves the chuck plate 12 and the probe plate 14together until the probe card 50 comes into contact with the wafer andthe stops are bottomed, with the stop height having been adjusted suchthat, when the stops are bottomed, the probe card 50 is pressed againstthe wafer 74 with the full probe actuation force. The alignment devicethus provides the entire probe actuation force. This “mechanical only”form of actuation is not preferred since the alignment device isrequired to provide the probe actuation force, which may be in the rangeof 100 to 1000 pounds, and is typically about 500 pounds.

Method 2

The alignment device moves the chuck plate 12 and the probe plate 14together until the probe card 50 comes into contact with the wafer, andthe movement of the alignment device is stopped before the stops arebottomed. Again, the stop height has been adjusted such that, when thestops are bottomed, the probe card 50 is pressed against the wafer 74with the full probe actuation force. The mechanical connecting devices90 are then actuated to complete the actuation of the cartridge and toprovide the entire probe actuation force. In this method, the alignmentdevice is only required to provide a percentage of the probe actuationforce. (for example, but not limited to, 1 to 10%,) to lock in the x andy relationships between the probe card 50 and the wafer during finalmovement of the chuck plate 12 and probe plate 14. Locking in theserelationships reduces the chance of misalignment during final actuation.

Methods 1 and 2 are “mechanical only” methods of actuation that have theadvantages that a) the probe card 50 is not required to be movablymounted to the probe plate and b) pneumatics/vacuum is not required toprovide the probe actuation force. These “mechanical only” actuationmethods are thus cheaper to implement than some of the other methods.

Method 3

The alignment device moves the chuck plate 12 and the probe plate 14together until the probe card 50 comes into contact with the wafer, andthe movement of the alignment device is stopped before the stops arebottomed. The mechanical connecting devices 90 are then actuated tobottom the stops. The area 72 behind the piston 64 is then pressurizedto provide the probe actuation force. In this method, the alignmentdevice is again only required to provide a percentage of the probeactuation force (for example, but not limited to, 1 to 10%,) to lock inthe x and y relationships between the probe card 50 and the wafer duringfinal z-movement of the chuck plate 12 and probe plate 14.

Method 4

The alignment device moves the chuck plate 12 and the probe plate 14together until the probe card 50 comes into contact with the wafer andthe stops are bottomed. The mechanical connecting devices 90 are thenactuated to lock the chuck plate 12 and the probe plate 14 together. Thearea 72 behind the piston 64 is then pressurized to provide the probeactuation force. In this method, the alignment device is again onlyrequired to provide a percentage of the probe actuation force (forexample, but not limited to, 1 to 10%,) to lock in the x and yrelationships between the probe card 50 and the wafer during finalz-movement of the chuck plate 12 and probe plate 14.

Method 5

The alignment device moves the chuck plate 12 and the probe plate 14together until the probe card 50 comes into contact with the wafer, andthe movement of the alignment device is stopped before the stops arebottomed. The mechanical connecting devices 90 are then actuated tobottom the stops. The pressure in the vicinity of the wafer 74 isreduced to provide the probe actuation force. In this method, thealignment device is again only required to provide a percentage of theprobe actuation force (for example, but not limited to, 1 to 10%,) tolock in the x and y relationships between the probe card 50 and thewafer during final z-movement of the chuck plate 12 and probe plate 14.

Method 6

The alignment device moves the chuck plate 12 and the probe plate 14together until the probe card 50 comes into contact with the wafer andthe stops are bottomed. The mechanical connecting devices 90 are thenactuated to lock the chuck plate 12 and the probe plate 14 together. Thepressure in the vicinity of the wafer 74 is reduced to provide the probeactuation force. In this method, the alignment device is again onlyrequired to provide a percentage of the probe actuation force (forexample, but not limited to, 1 to 10%,) to lock in the x and yrelationships between the probe card 50 and the wafer during finalz-movement of the chuck plate 12 and probe plate 14.

Applicants believe that methods 5 and 6 are the two, equally good,best-mode methods of locking the chuck plate 12 and the probe plate 14together and providing a probe actuation force.

Method 7

The alignment device moves the chuck plate 12 and the probe plate 14together until the stops are bottomed but without the probe card 50coming into contact with the wafer. The mechanical connecting devices 90are then actuated to lock the chuck plate 12 and the probe plate 14together. The area 72 behind the piston 64 is then pressurized toprovide the probe actuation force.

Method 8

The alignment device moves the chuck plate 12 and the probe plate 14together until the stops are bottomed but without the probe card 50coming into contact with the wafer. The mechanical connecting devices 90are then actuated to lock the chuck plate 12 and the probe plate 14together. The pressure in the vicinity of the wafer 74 is reduced toadvance the probe card 50 and to provide the probe actuation force.

When the mechanical connecting devices 90 draw the chuck plate 12 andthe probe plate 14 together to bottom the stops, appropriate controlelements are used to slow the rate of the clamping. The control elementsmay for example be orifices that are added to the pneumatic lines toslow the rate of venting.

Also, for the methods utilizing a pressure differential to provide ormaintain the probe actuation force, the cartridge 10 includes anautomatic valve in the appropriate nipple 31 for maintaining thepressure differential when disconnected, thereby to maintain the probeactuation force.

After the execution of one of the above methods, the cartridge is aself-contained and aligned probing and clamping device. The alignment ofthe wafer and the probe card is maintained as a result of the pressuredifferential across the piston 64 and/or the clamping force of themechanical connecting devices 90. Accordingly, no further externalalignment devices are required, and no external mechanism is requiredfor providing a clamping force or a probe actuation force duringburn-in. However, upon insertion into a burn-in chamber, connection istypically reestablished with the nipples 31 to provide maintenance ofthe pressure differential across the piston 64. This is done tocompensate for any leaks that might occur, and also to provide a meansfor controlling the probe actuation force, since the pressuredifferentials in the cartridge 10 will vary as the temperature of thecartridge 10 varies.

To provide the burn-in and/or test of the wafer, the cartridge 10 isplaced in a burn-in chamber. The burn-in chamber typically includes anumber of horizontally spaced positions for receiving cartridges in aspaced-apart stacked relationship. This permits burn-in of a number ofwafers to be done simultaneously.

To provide the burn-in and test of the wafer, it is necessary to engagethe connectors 46, 180, 182 with corresponding connectors in the burn-inchamber. To accomplish this engagement, a substantial insertion forcemay be required. The cartridge 10 and the burn-in chamber include aninsertion mechanism, whereby engagement of the respective electricalconnectors may be accomplished automatically, as discussed below withreference to FIGS. 20 to 24.

The insertion mechanism includes a cam follower arrangement 250, one ofwhich is provided on each side of the cartridge 10 as can be seen inFIG. 20. The cam follower arrangement includes a mounting block 252mounted to the probe plate 14 adjacent to the flange 40. The mountingblock 252 includes a transversely extending portion 254 and a shortshaft 256. Press-fitted to the shaft 256 is a ball-bearing 258.

The outer surface of the ball-bearing 258 is engaged in use by a camplate 260 that is shown in more detail in FIGS. 21 and 22.

The cam plate 260 includes two walls 262 and 264 that are located atright angles to one another. Between the walls 262, 264 at one end ofthe cam plate 258 is a collar 266 whereby the cam plate is connected toa pneumatic cylinder as will be discussed in more detail below. Formedin the wall 262 are four holes 268 by means of which the cam plate maybe mounted to a linear slide such as a cross roller bearing slide or alinear ball slide, also as discussed in more detail below. Formed in theouter surface of the wall 264 is at least one groove 270 that is sizedto receive the ball bearing 258 of a cartridge 10.

In the illustrated embodiment there are two grooves 270, but of courseit will be appreciated that the number of grooves 270 in the cam plate260 may be varied to accommodate a different number of cartridges 10.Applicants believe that a single cam plate 260 can comfortably beprovided with seven grooves, to enable seven cartridges to be engagedsimultaneously with their corresponding electrical connectors in aburn-in chamber.

Each groove 270 is defined by two cam surfaces 272 and 274. The camsurface 272 is used to advance the cartridge 10 into the burn-inchamber, thereby to engage the electrical connectors of the cartridgewith the corresponding connectors in the burn-in chamber. The camsurface 274 is used to retract the cartridge 10 to disengage theconnectors. For a maximum movement of 2.5 inch (64 mm) of the cam plate260 in the Z-direction, a ball bearing located in the groove (andconstrained to move in the Y-direction) will move approximately 0.35inch (9 mm,) to provide a mechanical advantage of approximately 7. Thatis, a force applied to the cam plate 264 in the Z-direction will resultin a force seven times as large being applied to the ball bearing in they direction.

Referring now to FIGS. 23 and 24, in use the cam plate 260 is connectedin the burn-in chamber to a pneumatic cylinder 276 via the collar 266.The pneumatic cylinder 276 is in turn mounted to a vertical bar 278 inthe burn-in chamber via a connecting block 280. The pneumatic cylinderhas a stroke of approximately 2.5″ and is used to move the cam plate inthe Z-direction. The cam plate 260 is slidably mounted to the bar 278 bymeans of a linear slide 282 that transfers lateral forces experienced bythe cam plate 260 to the bar 278 while permitting the cam plate to slidealong the bar 278 in the Z-direction. Mounted to the bar 278 is at leastone channel 281 for receiving the rail 32 of a cartridge 10.

The connection between the collar 266 of the cam plate 260 and thepneumatic cylinder 276 is shown in more detail in FIG. 23. Screwed intothe piston of the pneumatic cylinder 276 is a stud 284. The stud 284 hasscrew threads 286 defined in one end thereof for threaded engagementwith a bore formed in the piston of the pneumatic cylinder 276. At theother end, the stud 284 has a beveled head 288. The collar 266 includesa groove 290 for receiving a retaining ring 292. The collar 266 alsoincludes an internal ring 294. In assembled form, the collar alsoreceives a washer 296, two opposed beveled washers 298 and 300, and aspring washer 302. In use, when the piston of the pneumatic cylinder isadvanced, the head 288 of the stud 284 bears against the beveled washer298. The beveled washer 298 in turn bears against the washer 296, whichbears against the spring washer 302, which bears against the retainingring 292, which in turn transfers the actuating force of the pneumaticcylinder to the collar 266. When the piston of the pneumatic cylinder isretracted, the beveled head 288 bears against the beveled washer 300,which transfers the actuating force of the pneumatic cylinder 276 to thecollar 266. The components illustrated in FIG. 23 fit reasonably snuglytogether, with the spring washer providing sufficient play to allow somenutational misalignment between the stud 284 and the collar 266, and theclearances between the outer surfaces of the washers 298, 300 providingsufficient play to allow some sideways misalignment of the stud 286 andthe collar 266.

It will be appreciated that FIG. 24 shows only one half of thestructures and components required to support and engage the two sidesof a cartridge 10 in the burn-in chamber. A second set of identical, butmirror-image components is provided in the burn in chamber for receivingand engaging the other side of a cartridge 10.

In use, the cartridge 10 is slid horizontally, electrical connector endfirst, into the burn-in chamber, with the rails 32 fitting into thechannels 281 in the burn-in chamber. As the cartridge approaches itsfully inserted position, the alignment pins 48 enter correspondingalignment holes in the burn-in chamber. This serves to align theconnectors 46 with complementary electrical connectors provided in theburn-in chamber. At this time, the ball bearings 258 are received in theopen ends of the grooves of two opposed cam plates 260. The pistons ofthe pneumatic cylinders 276 are then advanced to provide the necessaryforces (via the cam plates 260) for engaging the electrical connectors46 on the cartridge with corresponding electrical connectors in theburn-in chamber. As mentioned previously, when engaged, the connectors46 protrude into a cooler section of the burn-in chamber through anaperture formed in a wall in the burn-in chamber. When the cartridge isfully inserted into the burn-in chamber, the flange 40 and seal 42 serveto close the aperture and isolate the cooler section (and hence theconnectors 46) from the hotter section of the burn-in chamber. Further,when the cartridge is fully inserted in the burn-in chamber, thechannels 22 of the cartridge 10 are aligned with air vents for providingcooling air, and external power and test signals can be applied to thewafer 74 via the connectors 46. Burn-in and test of the wafer thenprogresses as described in more detail in the concurrently filed,copending, commonly owned patent application entitled: “Wafer LevelBurn-in and Electrical Test System and Method” (Attorney Docket NumberAEHR-007/00US,) the disclosure of which is incorporated herein byreference.

Generally speaking, the temperature in the burn-in chamber is raised tothe required temperature, and power and timing, logic or other testsignals are applied to the wafer for the required burn-in duration. Itwill be noted however, that the cartridge may be used for otherwafer-level testing or burn-in methods. At the end of the burn-in and/ortest procedure, the pistons of the pneumatic cylinders 276 arewithdrawn, to disengage the electrical connectors 46 from the electricalconnectors in the burn-in chamber. The cartridge 10 is then removed fromthe burn-in chamber and placed in the alignment device (or a customfixture), and the wafer is then removed by retracting the piston 64 (andhence the probe card 50) from the wafer, then disengaging the mechanicalconnecting devices 90 and then lifting the probe plate 14 off the chuckplate 12 using the alignment device. A wafer-handling robot then removesthe wafer. In the cases where the probe card 50 is not movable, it maybe necessary for the alignment device or fixture to apply a compressiveforce to the cartridge 10 before the mechanical connecting devices aredisengaged.

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference. The inventionnow being fully described, it will be apparent to one of ordinary skillin the art that many changes and modifications can be made theretowithout departing from the spirit or scope of the appended claims.

What is claimed is:
 1. A kinematic coupling comprising: a male connectorcoupled to a first plate, of an electrical apparatus the male connectorincluding an undercut surface; and first and second opposed jaws coupledto a second plate, each of the jaws including a protruding lip and beingpivotally mounted to the second plate by a pivot pin and movable from aretracted position in which the male connector can be inserted betweenthe jaws and an engaging position in which the jaws prevent withdrawalof the male connector from between the jaws by engaging the undercutsurface of the male connector, wherein i) the jaws are biased towardstheir respective engaging positions by a force that is applied to thejaws at a position located on the same side of the pivot pin as theprotruding lip and ii) the jaws are moved by linearly translating aprobe along a direction that is substantially perpendicular totranslational movement by said jaws.
 2. A kinematic coupling accordingto claim 1, wherein said force is applied to the first and secondopposed jaws at a position located between said pivot pin and saidprotruding lip.
 3. A kinematic coupling according to claim 2, whereinthe probe is a key and the first and second jaws each include aninclined surface that can be acted upon by linearly translating the keyaway from said protruding lip to move the first and second jaws intotheir respective retracted positions.
 4. A kinematic coupling accordingto claim 1, wherein the male connector is movably coupled to the firstplate, and wherein, when the male connector is inserted between thefirst and second jaws and the first and second jaws are both in theirengaging positions, the male connector is movable relative to the firstplate between an extended position in which the engaging surface of themale connector is not in contact with the first and second jaws and aretracted position in which the engaging surface of the male connectoris in contact with the first and second jaws.
 5. A kinematic couplingaccording to claim 4, wherein the male connector is biased toward itsretracted position.
 6. A kinematic coupling according to claim 4 whereinthe male connector is moved into its extended position in use by meansof a pressure differential.
 7. A kinematic coupling according to claim 3wherein the first and second jaws make line contact with the engagingsurface of the male connector in use.
 8. A kinematic coupling accordingto claim 3 wherein the first and second jaws make point contact with theengaging surface of the male connector in use.
 9. A kinematic couplingaccording to claim 3 further comprising a first stop adjacent to themale connector, and a second stop adjacent to the jaws, wherein movementof the male connector towards its retracted position in use engages thejaws and pulls the first and second stops together.
 10. A kinematiccoupling according to claim 9 wherein at least one of the stops isadjustable in the direction of movement of the male connector.
 11. Akinematic coupling comprising: a male connector coupled to a firstplate, of an electrical apparatus the male connector including anundercut surface; and at least one jaw coupled to a second plate, the atleast one jaw including a protruding lip and being pivotally mounted tothe second plate by a pivot pin and movable from a retracted position inwhich the male connector can be received by the at least one jaw and anengaging position in which the at least one jaw prevents withdrawal ofthe male connector from the at least one jaw by engaging the undercutsurface of the male connector, wherein i) the at least one jaw is biasedtoward its respective engaging position by a force that is applied tothe at least one jaw at a position located on the same side of the pivotpin as the protruding lip and ii) the at least one jaw is moved bylinearly translating a probe along a direction that is substantiallyperpendicular to translational movement by said jaws.
 12. A kinematiccoupling according to claim 11, wherein the male connector is movablycoupled to the first plate, and wherein in use the male connector ismovable relative to the substrate between an extended position in whichthe engaging surface of the connector is not in contact with the atlease one jaw and a retracted position in which the engaging surface ofthe male connector is in contact with the at least one jaw.
 13. Akinematic coupling according to claim 12, wherein said force is appliedto the first and second opposed jaws at a position located between saidpivot pin and said protruding lip.
 14. A kinematic coupling according toclaim 12 wherein the male connector is moved into its extended positionin use by means of a pressure differential.
 15. A kinematic couplingaccording to claim 12 wherein the male connector makes line contact withthe at least one jaw.
 16. A kinematic coupling according to claim 12wherein the male connector makes point contact with at least one jaw.17. A kinematic coupling according to claim 12 further comprising afirst stop adjacent to the male connector; and a second stop adjacent tothe at least one jaw, wherein movement of the male connector towards itsretracted position in use engages the at least one jaw and pulls thefirst and second stops together.
 18. A kinematic coupling according toclaim 17 wherein at least one of the stops is adjustable in thedirection of movement of the male connector.
 19. A kinematic couplingaccording to claim 11, wherein the probe includes a spherical head andthe at least one jaw includes an inclined surface that can be acted uponby linearly translating the spherical head away from said protruding lipto move the at least one jaw into its retracted position.
 20. Acartridge comprising: a first plate; a probe card mounted to the firstplate; a second plate; a mechanism coupled to the second plate to hold asemiconductor wafer opposite to and available for electricalcommunication with the probe card; a kinematic coupling included, a maleconnector coupled to one of the first or second plates including anundercut surface; and first and second opposed jaws coupled to the otherof said first and second plates, each of the jaws including a protrudinglip and being pivotally mounted to a chuck plate by a pivot pin andmovable from a retracted position in which the male connector can beinserted between the jaws and an engaging position in which the jawsprevent withdrawl of the male connector from between the jaws byengaging the undercut surface of the male connector, wherein the jawsare biased towards their respective engaging positions by a mechanismthat provides an inwardly directed force that is applied to the jaws ata position located on the same side of the pivot pin as the protrudinglip.
 21. The cartridge of claim 20, wherein the jaws are moved bylineraly translating a probe along a direction that is substantiallyperpendicular to tranlational movement by said jaws.
 22. A cartridgecomprising: a first plate; a probe card mounted to the first plate; asecond plate; a mechanism coupled to the second plate to hold asemiconductor wafer opposite to and available for electricalcommunication with the probe card; kinematic coupling including, a maleconnector coupled to one of the first or second plates including anundercut surface; and first and second opposed jaws coupled to the otherof said first and second plates, each of the jaws movable from theretracted position in which the male connector can be inserted betweenthe jaws and an engaging position in which the jaws prevent withdrawl ofthe male connector from between the jaws by engaging the male connector;wherein the kinematic coupling is configured to be engaged over a rangeof relative lateral movement of the first and second plates in a firststate and not engaged in the range of relative lateral movement of thefirst and second plates in a second state.
 23. The cartridge of claim22, wherein the jaws have protruding lips, the male connector has anundercut surface and a neck adjacent to the undercut surface and maleconnector has a neck adjacent to the undercut surface and the kinematiccoupling has a clearance between the protruding lips of the jaws and theneck, the clearance permitting the kinetic coupling to be engaged overthe range of relative lateral movement of the first and second plates inthe first state.
 24. The cartridge of claim 22, wherein the range ofrelative lateral movement is less than +/−1.27 millimeters.
 25. Thecartridge of claim 22 wherein the mechanism coupled to the second plateto hold a semiconductor wafer comprises a pedestal including vacuumgrooves.
 26. The cartridge of claim 22, wherein the kinematic couplingincludes a mechanism to provide a retracting force on the male connectorperpendicular to the lateral movement in the second state, preventingthe lateral movement in the second state.
 27. The cartridge of claim 26,wherein the retracting force is between 735 and 1020 N.
 28. Thecartridge of claim 26, wherein the mechanism to provide the retractingforce comprises a spring.
 29. The cartridge of claim 28, wherein themale connector is moved into its extended position in use by means of apressure differential.